Cyclosporine is the most widely used immunosuppressive agent in transplantation, however it has been demonstrated that it causes a decrease in glomerular filtration rate and ERPF while there is an increase in renal vascular resistance and mean arterial pressure. It is believed that FK-506 may also cause some of the same side effects. Clinical data suggests that while FK-506 may alter renal hemodynamics in a similar fashion, mean arterial pressure remains unchanged. The degree to which FK-506 affects renal and systemic parameters as compared to Cyclosporine is still unknown.